As electronic systems have increased in complexity, attempts have been made to increase the amount of electronic circuitry contained in a given amount of space. One existing approach is to mount integrated circuits on a circuit board and cover them with an cover. The cover provides physical protection for the integrated circuits and serves as a heat spreader to help dissipate heat from the integrated circuits. An existing integrated circuit cover does not accommodate height variations of mounted integrated circuits. Consequently, a variety of integrated circuit covers, each corresponding to a different integrated circuit height must be available, with the appropriate integrated circuit cover selected and installed over the integrated circuits after the mounted integrated circuit has been determined. This variety of integrated circuit covers results in complicated production and inventory issues.
FIG. 1 is a cross-sectional view diagram illustrating an example of an assembly incorporating an existing integrated circuit cover. The assembly includes a circuit board 101. Circuit board 101 has a first surface 114 and a second surface 115. Integrated circuit 106 is mounted on first surface 114 of circuit board 101 via connections 107. Integrated circuit 108 is mounted on first surface 114 of circuit board 101 via connections 109. Integrated circuit 110 is mounted on first surface 114 of circuit board 101 via connections 111. Integrated circuit 112 is mounted on first surface 114 of circuit board 101 via connections 113.
Integrated circuit cover 102 covers integrated circuits 106, 108, 110, and 112, and is attached to circuit board 101 via fasteners 104 and 105. Thermally conductive material 103 fills gaps between integrated circuits 106, 108, 110, and 112 and integrated circuit cover 102. A certain amount of pressure of integrated circuit cover 102 against thermally conductive material 103 is desirable to ensure good contact with integrated circuits 106, 108, 110, and 112 so as to promote heat transfer from integrated circuits 106, 108, 110, and 112 to integrated circuit cover 102. However, the geometry of the assembly results in pressure being localized near fasteners 104 and 105. Since some integrated circuits are closer to fasteners 104 and 105 than other integrated circuits, the pressure exerted against integrated circuits 106, 108, 110, and 112 is unequal. The inequality of pressure can affect heat transfer and limits the amount of pressure that may be applied without causing excessive pressure to be placed on integrated circuits near fasteners 104 and 105. As can be seen from FIG. 1, integrated circuit cover 102 tends to bow outward. Depending on the rigidity of circuit board 101, circuit board 101 may tend to bow outward, away from the cover, resulting in surface 115 of circuit board 101 being displaced to position 116. Thus, even when an integrated circuit cover of a particular height is selected, dimensional distortion of the integrated circuit cover can result in uneven thermal conductivity and reduced performance.
Therefore, a integrated circuit cover is needed that avoids the need to produce and maintain in inventory covers of different heights. An integrated circuit cover is needed that provides even thermal performance over a large area, for example, over multiple integrated circuits.